mirror of https://github.com/M66B/FairEmail.git
387 lines
18 KiB
Java
387 lines
18 KiB
Java
package eu.faircode.email;
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/*
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This file is part of FairEmail.
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FairEmail is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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FairEmail is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FairEmail. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2018-2024 by Marcel Bokhorst (M66B)
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*/
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import android.content.Context;
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import android.graphics.Bitmap;
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import android.graphics.Color;
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import android.net.Uri;
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import android.text.TextUtils;
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import android.util.Pair;
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import org.bouncycastle.asn1.ASN1Sequence;
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import org.bouncycastle.asn1.ASN1TaggedObject;
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import org.bouncycastle.asn1.DERIA5String;
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import org.bouncycastle.asn1.x509.Extension;
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import org.bouncycastle.cert.jcajce.JcaX509ExtensionUtils;
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import org.bouncycastle.util.io.pem.PemObject;
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import org.bouncycastle.util.io.pem.PemReader;
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import java.io.ByteArrayInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.net.MalformedURLException;
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import java.net.URL;
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import java.security.KeyStore;
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import java.security.cert.CertPathBuilder;
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import java.security.cert.CertPathBuilderResult;
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import java.security.cert.CertPathValidator;
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import java.security.cert.CertStore;
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import java.security.cert.CertStoreParameters;
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import java.security.cert.Certificate;
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import java.security.cert.CertificateFactory;
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import java.security.cert.CollectionCertStoreParameters;
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import java.security.cert.PKIXBuilderParameters;
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import java.security.cert.TrustAnchor;
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import java.security.cert.X509CertSelector;
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import java.security.cert.X509Certificate;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.Enumeration;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Locale;
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import java.util.Map;
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import java.util.Set;
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import javax.net.ssl.HttpsURLConnection;
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// Brand Indicators for Message Identification (BIMI)
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// https://bimigroup.org/
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public class Bimi {
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// Beam me up, Scotty
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private static final int CONNECT_TIMEOUT = 10 * 1000; // milliseconds
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private static final int READ_TIMEOUT = 15 * 1000; // milliseconds
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private static final String OID_BrandIndicatorforMessageIdentification = "1.3.6.1.5.5.7.3.31";
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private static final List<String> DMARC_POLICIES = Collections.unmodifiableList(Arrays.asList(
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"quarantine", "reject"
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));
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static Pair<Bitmap, Boolean> get(
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Context context, String _domain, String selector, int scaleToPixels)
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throws IOException {
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Bitmap bitmap = null;
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boolean verified = false;
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if (TextUtils.isEmpty(selector))
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selector = "default";
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// Get DNS record
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String domain = _domain;
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DnsHelper.DnsRecord record = lookupBimi(context, selector, domain);
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if (record == null) {
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String parent = UriHelper.getParentDomain(context, domain);
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if (parent == null)
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return null;
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domain = parent;
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record = lookupBimi(context, selector, domain);
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if (record == null)
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return null;
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}
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// Process DNS record
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Map<String, String> values = MessageHelper.getKeyValues(record.response);
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List<String> tags = new ArrayList<>(values.keySet());
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Collections.sort(tags); // process certificate first
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for (String tag : tags) {
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switch (tag) {
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// Version
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case "v": {
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String version = values.get(tag);
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if (!"BIMI1".equalsIgnoreCase(version))
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Log.w("BIMI unsupported version=" + version);
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break;
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}
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// Image link
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case "l": {
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if (bitmap != null)
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continue;
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String l = values.get(tag);
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if (TextUtils.isEmpty(l))
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continue;
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try {
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Uri ul = Uri.parse(l);
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if (!"https".equals(ul.getScheme()))
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throw new MalformedURLException(l);
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URL url = new URL(l);
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Log.i("BIMI favicon " + url);
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HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();
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connection.setRequestMethod("GET");
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connection.setReadTimeout(READ_TIMEOUT);
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connection.setConnectTimeout(CONNECT_TIMEOUT);
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connection.setInstanceFollowRedirects(true);
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ConnectionHelper.setUserAgent(context, connection);
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connection.connect();
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try {
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bitmap = ImageHelper.renderSvg(connection.getInputStream(),
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Color.WHITE, scaleToPixels);
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} finally {
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connection.disconnect();
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}
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} catch (MalformedURLException ex) {
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Log.i(ex);
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}
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break;
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}
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// Certificate link
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case "a": {
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if (verified)
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continue;
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String a = values.get(tag);
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if (TextUtils.isEmpty(a))
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continue;
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try {
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Uri ua = Uri.parse(a);
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if (!"https".equals(ua.getScheme()))
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throw new MalformedURLException(a);
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URL url = new URL(a);
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Log.i("BIMI PEM " + url);
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HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();
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connection.setRequestMethod("GET");
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connection.setReadTimeout(READ_TIMEOUT);
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connection.setConnectTimeout(CONNECT_TIMEOUT);
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connection.setInstanceFollowRedirects(true);
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ConnectionHelper.setUserAgent(context, connection);
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connection.connect();
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// Fetch PEM objects
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List<PemObject> pems = new ArrayList<>();
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try {
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InputStreamReader isr = new InputStreamReader(connection.getInputStream());
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PemReader reader = new PemReader(isr);
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while (true) {
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PemObject pem = reader.readPemObject();
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if (pem == null)
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break;
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else
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pems.add(pem);
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}
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} finally {
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connection.disconnect();
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}
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if (pems.size() == 0)
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throw new IllegalArgumentException("No PEM objects");
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// Convert to X.509 certificates
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List<X509Certificate> certs = new ArrayList<>();
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CertificateFactory fact = CertificateFactory.getInstance("X.509");
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for (PemObject pem : pems) {
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ByteArrayInputStream bis = new ByteArrayInputStream(pem.getContent());
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X509Certificate cert = (X509Certificate) fact.generateCertificate(bis);
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Log.i("BIMI cert" +
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" serial=" + cert.getSerialNumber() +
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" issuer=" + cert.getIssuerDN() +
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" subject=" + cert.getSubjectDN() +
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" not before=" + cert.getNotBefore() +
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" not after=" + cert.getNotAfter());
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certs.add(cert);
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}
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// Get first certificate
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// https://datatracker.ietf.org/doc/draft-fetch-validation-vmc-wchuang/
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X509Certificate cert = certs.remove(0);
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// Check certificate type
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List<String> eku = cert.getExtendedKeyUsage();
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if (!eku.contains(OID_BrandIndicatorforMessageIdentification))
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throw new IllegalArgumentException("Invalid certificate type");
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// Check subject
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boolean found = false;
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String root = UriHelper.getRootDomain(context, domain);
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List<String> names = EntityCertificate.getDnsNames(cert);
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for (String name : names)
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if (root != null &&
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root.equalsIgnoreCase(UriHelper.getRootDomain(context, name))) {
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found = true;
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break;
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}
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if (!found)
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throw new IllegalArgumentException("Invalid certificate" +
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" domain=" + domain +
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" names=" + TextUtils.join(", ", names));
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// https://datatracker.ietf.org/doc/html/rfc3709#page-6
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// LogotypeExtn ::= SEQUENCE {
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// subjectLogo [2] EXPLICIT LogotypeInfo OPTIONAL,
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// LogotypeInfo ::= CHOICE {
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// direct [0] LogotypeData,
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// LogotypeData ::= SEQUENCE {
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// image SEQUENCE OF LogotypeImage OPTIONAL,
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// LogotypeImage ::= SEQUENCE {
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// imageDetails LogotypeDetails,
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// LogotypeDetails ::= SEQUENCE {
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// mediaType IA5String,
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// logotypeHash SEQUENCE SIZE (1..MAX) OF HashAlgAndValue,
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// logotypeURI SEQUENCE SIZE (1..MAX) OF IA5String }
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try {
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byte[] logoType = cert.getExtensionValue(Extension.logoType.getId());
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ASN1Sequence logotypeExtn =
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(ASN1Sequence) (ASN1Sequence) JcaX509ExtensionUtils.parseExtensionValue(logoType);
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for (int i = 0; i != logotypeExtn.size(); i++) {
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ASN1TaggedObject subjectLogo = ASN1TaggedObject.getInstance(logotypeExtn.getObjectAt(i));
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if (subjectLogo.getTagNo() == 2) {
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ASN1TaggedObject logotypeInfo = (ASN1TaggedObject) subjectLogo.getBaseObject();
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if (logotypeInfo.getTagNo() == 0) {
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ASN1Sequence logotypeData = (ASN1Sequence) logotypeInfo.getBaseObject();
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ASN1Sequence logotypeImage = (ASN1Sequence) logotypeData.getObjectAt(0);
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ASN1Sequence logotypeDetails = (ASN1Sequence) logotypeImage.getObjectAt(0);
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DERIA5String mediaType = (DERIA5String) logotypeDetails.getObjectAt(0);
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Log.i("BIMI media type=" + mediaType.getString());
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ASN1Sequence logotypeURI = (ASN1Sequence) logotypeDetails.getObjectAt(2);
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DERIA5String uri = (DERIA5String) logotypeURI.getObjectAt(0);
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Log.i("BIMI log uri=" + uri.getString());
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String mimeType = ImageHelper.getDataUriType(uri.getString());
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if ("image/svg+xml".equalsIgnoreCase(mimeType)) {
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InputStream is = ImageHelper.getDataUriStream(uri.getString());
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bitmap = ImageHelper.renderSvg(is, Color.WHITE, scaleToPixels);
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Log.i("BIMI URI image=" + bitmap.getWidth() + "x" + bitmap.getHeight());
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}
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}
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break;
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}
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}
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} catch (Throwable ex) {
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Log.e(ex);
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}
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// Get trust anchors
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Set<TrustAnchor> trustAnchors = new HashSet<>();
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// Get root certificates from assets
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for (String ca : context.getAssets().list("vmc"))
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if (ca.endsWith(".pem")) {
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Log.i("BIMI reading ca=" + ca);
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try (InputStream is = context.getAssets().open("vmc/" + ca)) {
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X509Certificate c = (X509Certificate) fact.generateCertificate(is);
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trustAnchors.add(new TrustAnchor(c, null));
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}
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}
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// Get root certificates from key store
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KeyStore ks = KeyStore.getInstance("AndroidCAStore");
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ks.load(null, null);
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Enumeration<String> aliases = ks.aliases();
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while (aliases.hasMoreElements()) {
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String alias = aliases.nextElement();
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Certificate c = ks.getCertificate(alias);
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if (c instanceof X509Certificate)
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trustAnchors.add(new TrustAnchor((X509Certificate) c, null));
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}
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// Validate certificate
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X509CertSelector target = new X509CertSelector();
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target.setCertificate(cert);
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PKIXBuilderParameters pparams = new PKIXBuilderParameters(trustAnchors, target);
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CertStoreParameters intermediates = new CollectionCertStoreParameters(certs);
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pparams.addCertStore(CertStore.getInstance("Collection", intermediates));
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pparams.setRevocationEnabled(false);
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pparams.setDate(null);
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CertPathBuilder builder = CertPathBuilder.getInstance("PKIX");
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CertPathBuilderResult path = builder.build(pparams);
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CertPathValidator cpv = CertPathValidator.getInstance("PKIX");
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cpv.validate(path.getCertPath(), pparams);
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Log.i("BIMI valid domain=" + domain);
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// Get DMARC record
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String txt = "_dmarc." + domain;
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Log.i("BIMI fetch TXT " + txt);
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DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, txt, "txt");
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if (records.length == 0) {
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String parent = UriHelper.getParentDomain(context, domain);
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if (parent != null) {
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txt = "_dmarc." + parent;
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records = DnsHelper.lookup(context, txt, "txt");
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}
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}
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if (records.length == 0)
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throw new IllegalArgumentException("DMARC missing");
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Log.i("BIMI got TXT " + records[0].response);
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Map<String, String> dmarc = MessageHelper.getKeyValues(records[0].response);
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String p = dmarc.get("p");
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if (p == null ||
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!DMARC_POLICIES.contains(p.toLowerCase(Locale.ROOT)))
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throw new IllegalArgumentException("DMARC invalid p=" + p);
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String pct = dmarc.get("pct");
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if (!TextUtils.isEmpty(pct) && !"100".equals(pct))
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throw new IllegalArgumentException("DMARC invalid pct=" + p);
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Log.i("BIMI verified");
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verified = true;
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} catch (MalformedURLException ex) {
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Log.i(ex);
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} catch (Throwable ex) {
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Log.w(new Throwable("BIMI " + _domain, ex));
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}
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break;
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}
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default:
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Log.w("BIMI unknown tag=" + tag);
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}
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}
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return (bitmap == null ? null : new Pair<>(bitmap, verified));
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}
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private static DnsHelper.DnsRecord lookupBimi(Context context, String selector, String domain) {
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try {
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String txt = selector + "._bimi." + domain;
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Log.i("BIMI fetch TXT " + txt);
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DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, txt, "txt");
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if (records.length == 0)
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return null;
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Log.i("BIMI got TXT " + records[0].response);
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return records[0];
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} catch (Throwable ex) {
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Log.i(ex);
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return null;
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}
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}
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}
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